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105 lines
2.3 KiB
Plaintext
105 lines
2.3 KiB
Plaintext
#include "avr/delay.h"
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void setup() {
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pinMode(11, OUTPUT);
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// Set up Timer 2 to do pulse width modulation on the speaker
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// pin.
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// Use internal clock (datasheet p.160)
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ASSR &= ~(_BV(EXCLK) | _BV(AS2));
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// Set fast PWM mode (p.157)
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TCCR2A |= _BV(WGM21) | _BV(WGM20);
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TCCR2B &= ~_BV(WGM22);
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// Do non-inverting PWM on pin OC2A (p.155)
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// On the Arduino this is pin 11.
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TCCR2A = (TCCR2A | _BV(COM2A1)) & ~_BV(COM2A0);
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TCCR2A &= ~(_BV(COM2B1) | _BV(COM2B0));
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// No prescaler (p.158)
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TCCR2B = (TCCR2B & ~(_BV(CS12) | _BV(CS11))) | _BV(CS10);
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// Set initial pulse width to the first sample.
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OCR2A = 0;
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}
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int play (uint16_t f, uint8_t T) {
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sendKarplusStrongSound(f, T);
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}
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// http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1249193795
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int sendKarplusStrongSound(const uint16_t f /*Hz*/, const uint8_t T /*sec*/) {
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const uint8_t N = 32;
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const uint32_t sr = f * N; // sample rate: 800(25Hz)..47619(1488Hz)
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int16_t buf[N];
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for (uint8_t i=0; i<N; i++)
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buf[i] = (int16_t) random(-32768,32767);
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uint8_t bh = 0;
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const int Tloop = 60; // or is it more?
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const int dt = 16000000/sr - Tloop;
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for (uint32_t i=sr*T/2; i>0; i--) {
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const int8_t v = (int8_t) (buf[bh] >> 8);
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OCR2A = v;
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_delay_us(dt); // or do something else for <dt> usecs
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uint8_t nbh = bh!=N-1 ? bh+1 : 0;
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int32_t avg = buf[bh] + (int32_t)buf[nbh];
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//avg = (avg << 10) - avg; // subtract avg more than once to get faster volume decrease
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avg = (avg << 10) - avg -avg;
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buf[bh] = avg >> 11; // no division, just shift
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bh = nbh;
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}
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}
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// Frequencies (in Hz) of notes
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#define FSH_4 370
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#define A_4 440
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#define B_4 494
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#define E_4 330
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#define CSH_5 554
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#define D_5 587
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#define FSH_5 740
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#define CSH_4 277
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#define GSH_4 415
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#define REST 0
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void loop() {
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// Axel F
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play(FSH_4, 2);
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play(REST, 2);
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play(A_4, 3);
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play(FSH_4, 2);
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play(FSH_4, 1);
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play(B_4, 2);
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play(FSH_4, 2);
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play(E_4, 2);
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play(FSH_4, 2);
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play(REST, 2);
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play(CSH_5, 3);
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play(FSH_4, 2);
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play(FSH_4, 1);
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play(D_5, 2);
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play(CSH_5, 2);
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play(A_4, 2);
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play(FSH_4, 2);
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play(CSH_5, 2);
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play(FSH_5, 2);
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play(FSH_4, 1);
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play(E_4, 2);
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play(E_4, 1);
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play(CSH_4, 2);
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play(GSH_4, 2);
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play(FSH_4, 6);
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play(REST, 12);
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delay(100);
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}
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